Calculation method for sunshine duration in canopy gaps and its application in analyzing gap light regimes

Understory light is essential to the growth and survival of plants, yet the light varies temporally and spatially within forest gaps. Measurement of understory light levels using light sensors is both time and labor intensive. Sunshine duration (SD) has a strong correlation with solar radiation and has been the variable most widely used for estimating solar radiation. The power of SD-based methods for estimating solar radiation lies in its ability to quickly estimate light levels. Although several calculation methods for SD within canopy gaps are available, all the methods oversimplify canopy gaps by classifying them as cylindrical or ellipsoid and thus have a relatively low level of accuracy. In this study we developed a calculation method for SD at any given point within natural canopy gaps and we used SD to estimate solar radiation within 12 canopy gaps on Mt. Taibai in China based on the Angström-Prescott model. We then evaluated the SD-based solar radiation by the total and direct solar radiation derived from a gap light index based on hemispherical photographs (HP). Finally, we analyzed the spatial-temporal characteristics of light levels within these 12 gaps by using the solar radiation derived from SD at hundreds of simulated points in each gap. Our results showed that (1) SD-based solar radiation was not statistically different from HP-based direct solar radiation and had a strong linear correlation with HP-based total solar radiation; (2) growing-season daily mean solar radiation within the 12 gaps varied from 0.08 to 13.28 MJ m⁻² day⁻¹ with an average of 4.13 MJ m⁻² day⁻¹; (3) solar radiation had a positive correlation with the ratio of the square root of the canopy gap area to the mean canopy height. This relationship was significant but solar radiation had no correlation with the canopy gap area; (4) among most gaps solar radiation was greatest in May while potential SD was longest in June 2008. From these results we can conclude that the SD-based method for estimating solar radiation developed in this study can quickly and accurately estimate light levels at any specified point within canopy gaps. SD-based solar radiation appears to be a good choice for studies on the spatial-temporal characteristics of gap light levels.     

Tropical reptiles in pine forests: Assemblage responses to plantations and plantation management by burning

Worldwide, the land area devoted to timber plantations is expanding rapidly, especially in the tropics, where reptile diversity is high. The impacts of plantation forestry and its management on native species are poorly known, but are important, because plantation management goals often include protecting biodiversity. We examined the impact of pine (Pinus caribaea) plantations, and their management by fire, on the abundance and richness of reptiles, a significant proportion of the native biodiversity in tropical northern Australia, by (i) comparing abundance and diversity of reptiles among pine plantations (on land cleared specifically for plantation establishment), and two adjacent native forest types, eucalypt and Melaleuca woodlands, and (ii) comparing reptile abundance and richness in pine forest burnt one year prior to the study to remove understorey vegetation with pine forest burnt two years prior to the study. We also examined the influence of fire on reptile assemblages in native vegetation, by comparing eucalypt woodland burnt two years prior to the study and unburnt for eight years. To quantify mechanisms driving differences in reptile richness and abundance among forest types and management regimes, we measured forest structure, the temperatures used by reptiles (operative temperature) and solar radiation, at replicate sites in all forest types and management regimes. Compared to native forests, pine forests had taller trees, lower shrub cover in the understorey, more and deeper exotic litter (other than pine), and were cooler and shadier. Reptile assemblages in pine forests were as rich as those in native forests, but pine assemblages were composed mainly of species that typically use closed-canopy rainforest and prefer cooler, shadier habitats. Burning did not appear to influence the assemblage structure of reptiles in native forest, but burning under pine was associated with increased skink abundance and species richness. Burned pine was not warmer or sunnier than unburned pine, a common driver of reptile abundance, so the shift in lizard use after burning may have been driven by structural differences in understorey vegetation, especially amounts of non-native litter, which were reduced by burning. Thus, burning for management under pine increased the abundance and richness of lizard assemblages using pine. Pine plantations do not support the snake diversity common to sclerophyllous native forests, but pine may have the potential to complement rainforest lizard diversity if appropriately managed.     

椴木光变色前后碳价态变化初探

利用紫外光照射椴木单板,采用X射线光电子能谱仪（XPS）分析光变色前后碳价态的变化情况。结果表明,C1和C2随着光照时间的增长,呈现出下降的趋势;C3和C4随着光照时间的增长,呈现上升的趋势。     

日本落叶松容器苗造林研究

通过对日本落叶松裸根苗、轻基质容器苗和黑塑料杯容器苗的苗木质量及造林效果的对比研究得出,轻基质容器育苗能够显著提高落叶松的苗高、地径及一级侧根数量,苗木质量较高;在不同立地条件下,采用轻基质容器苗造林能够显著提高造林成活率及造林苗的新梢生长量,是适宜在冀北山区推广的造林技术。     

不同生长期燕子掌SOD含量与环境因子的关系

研究了不同生长时期燕子掌叶和花中SOD的含量及不同环境因子下燕子掌叶中SOD的含量。结果表明:随着燕子掌由营养生长向生殖生长转变,叶中SOD的含量会升高,花比叶中含量高;在不同盐浓度、水分、光照处理下,燕子掌叶中SOD的活性会随着3种处理水平的增加而升高到一定峰值后下降;3种环境因子对燕子掌的影响程度由大到小依次是盐光照水分。     

不同逆境因子对吊兰叶绿体色素含量的影响

研究了不同浓度NaCl、水分、光照条件下叶片全绿的吊兰叶中叶绿体色素的含量。结果表明:在不同盐浓度和干旱胁迫下,吊兰叶中叶绿体色素的含量总体呈下降趋势。强光照利于叶绿体色素的合成。综合3种环境因子的结果,吊兰对干旱最为敏感;NaCl其次,浓度超过200 mmol/L影响其叶绿体色素的合成;对光照的耐受范围广,要求不严格。     

不同枝量类型富士苹果光强分布及产量品质比较

对陇东改良纺锤形富士苹果3种枝量类型树冠内相对光照强度、树冠不同部位光照分布特征、果实产量、产量分布特征及品质进行了对比研究。结果表明:枝量过多型树冠内小于30%的相对光照强度比例最大,枝量合理型次之,枝量不足型最小。枝量合理型、枝量不足型、枝量过多型小于30%的相对光照体积所占树冠总体积分别为32.23%、24.19%、49.53%;产量分别为3 195、1 555、2 098 kg/667m2;果实品质各项指标枝量不足型略高于枝量合理型,但二者均达到了优质苹果的要求,确定出陇东地区富士苹果优质高产的最适留枝量为84 000/667m2左右。     

不同光照条件对一串红“猩红皇后”幼苗生长的影响

通过搭建黑色网纱对一串红新品种"猩红皇后"的幼苗进行了不同光照强度的试验。结果表明:不同光照条件对一串红幼苗的株高、地径、叶量、叶面积、茎叶及根系的鲜干重有不同影响,遮光率为60%左右有利于幼苗的株高、地径、叶片数、叶面积的增长,也有利于根系的生长;遮光率为90%以上对幼苗生长有负作用;不同遮光处理对幼苗生长的影响发生明显变化在1周以后,18 d后60%遮光处理组与70%相比生长优势明显。     

^60Co-γ射线对不同柑橘品种的辐射效应

以稻叶温州蜜柑（Citrus unshiu var.Inaba）、福橘（C.reticualta var.Fuju）、玫瑰橙（C.sinensis var.Meiguicheng）、华红（C.sinensis var.Huahong Newhall）和早金（C.sinensis var.Earlygold）等5个柑橘品种的接穗为试材,进行^60Co-γ射线照射处理,结合常规压片法,研究^60Co-γ射线对不同柑橘品种接穗的嫁接成活率及细胞有丝分裂行为的影响。结果表明：辐射累积剂量为2000R时,接穗嫁接成活率因品种不同而异,其中稻叶温州蜜柑的嫁接成活率最高（69.89%）,福橘次之,橙类较低（华红最低为32%）;^60Co-γ射线处理可诱发细胞有丝分裂异常,其诱变效应因柑橘品种不同而有所差别,柑类与橘类的有丝分裂异常率明显高于橙类。     

茶园主要害虫种群灯下监测及频振式与LED式杀虫灯的效果评价

试验结果表明,虫情测报灯对茶树鳞翅目（尺蠖蛾科、斑蛾科、鹿蛾科、卷叶蛾科、细蛾科、蓑蛾科、豹蠹蛾科、毒蛾科、剌蛾科、螟蛾科、镰蛾科等）、鞘翅目(金龟甲科、天牛科等)、直翅目（蝗虫科、蝼蛄科、蟋蟀科等）、同翅目（叶蝉科、蛾蜡蝉科）、等翅目具有良好的诱集作用,初步明确了白蚁、金龟甲、卷叶蛾类、茶银尺蠖、茶尺蠖、油桐尺蠖、茶斑蛾、茶鹿蛾、茶白纹螟、黑跗眼天牛、茶天牛、红翅天牛等害虫的灯下年消长规律,其中部分害虫的发生规律和世代数与文献记录存在差异。LED红光杀虫灯对昆虫没有诱集作用,蓝光杀虫灯诱虫能力强于紫光杀虫灯,其中,紫光杀虫灯诱集鳞翅目能力强于蓝光杀虫灯,诱集茶树鞘翅目害虫和天敌的能力也强于蓝光杀虫灯,而蓝光杀虫灯诱集半翅目、双翅目、同翅目和蜉蝣目昆虫的能力则比紫光杀虫灯强,频振灯除了诱集中性昆虫（蚊虫和蜉蝣）的能力比蓝光杀虫灯差外,对茶树害虫和天敌的诱集能力均大大优于紫光杀虫灯和蓝光杀虫灯,尤其对天敌有很强的杀伤力。而且,频振灯的诱虫谱比紫光杀虫灯和蓝光杀虫灯更宽。